Cell Structure and Diversity

Unicellular

organism consists of just one cell

Multicellular

organism consist of lots of cells

Eukaryotic cells

Contain a nucleus and membrane bound organelles

Prokaryotic cells

Do not contain a nucleus and membrane bound organelles

Organelles

Structures within cells which carry out a particular role

Cytoplasm function

Contents of the cell, except the nucleus.Act as a medium for chemical reactions to take place inside the cell.

Cytosol

Liquid part of the cytoplasm

Semi-permeable

How a membrane allows some small molecules pass through it

Selectively permeable

How a cell membrane actively controls the entry and exit of materials in a cell

Nucleus

Control centre of the cell. It contains DNA found in structures called chromosomes. Nucleolus function is to make a type of RNA

Chromatin

Consists of DNA wrapped around proteins called histones

Chromosome

Condensed, wound-up chromatin

Genes

Sections of DNA in chromosomes that carry instructions for making proteins

Mitochondria function

responsible for cellular respiration, the release of energy from food, converting into ATP

Ribosomes function

Responsible for protein synthesis. Building various proteins needed to regulate the cell’s metabolism or build an organisms tissue

Endoplasmic reticulum function

Responsible for protein and lipid synthesis. Production site for important cellular fats, like phospholipids and cholesterol. Also stores and releases calcium

Rough Endoplasmic Reticulum

Covered in ribosomes. Site of protein synthesis

Smooth Endoplasmic Reticulum

No Ribosomes

Golgi apparatus function

Responsible for packaging protein and lipids manufactured in the ER and moving them to other parts of the cell or outside the cell. Produce carbohydrates needed to build cell walls in the plant cell

Cell wall function

Provides strength and support to the cell. Prevents cell from bursting if it absorbs too much water.

Fully permeable

All substances can pass through

Middle lamella

Space between the cell walls of two cells

Chloroplasts function

Responsible to make food for plant cells during the process of photosynthesis.

Vacuole function

Give plant cell strength, pushing against cell wall from the inside

Turgor

Internal pressure exerted by the large vacuole on the cell walls.

Specialised cells

Have altered structures to match their specific function

Tissue

Group of similar specialised cells, carrying out a specific function

Organ

Group of different tissues working together to perform a specific function

Organ system

Multiple organs co-operating to carry out a specific function

Stem cells

Unspecialised cells in the body

Cell membrane structure

Made up of two layers of phospholipids, known as lipid bilayer. Proteins are embedded in this bilayer, providing support and acting as special channels to control what comes in and out of the cell.

Nucleus structure

Wrapped in a phospholipid membrane, which has small openings called nuclear pores, these allow materials to pass in and out of nucleus like RNA. When cell doesn’t divide, DNA is sprawled and turns into chromatin. Just before cell divides, DNA turns into chromosomes.

Mitochondria structure

Contains an outer membrane and a inner membrane folded into structures called cristae. The more folds in the inner membrane, the more energy it can release.

Ribosomes structure

Made of ribosomal RNA and proteins, they are not surrounded by a membrane

Endoplasmic Reticulum structure

Consists of interconnected tubes called cisternae

Golgi apparatus structure

Consists of stacks of membrane-bound sacs called cisternae which are not interconnected.

Cell wall structure

Made from a complex carbohydrate called cellulose. The middle lamella contains a substance called pectin which holds the cells together

Chloroplasts structure

Contain a double membrane, inner membrane is not folded and contain a loop of DNA. Inside there is a liquid called the storms and stacks of green pancake-like structures called thylakoid. Stack of thylakoids is called a granum.

Vacuole structure

Filled with a fluid called cell sap. Sap contains water, dissolved sugars and salts and waste materials.

Types of stem cells

Pluripotent stem cells and Multipotent stem cells